(Not applicable.)
1. Field of the Invention
The present invention relates to an applicator and method of applying multiple fluid sealant agents to a work surface and is particularly, although not exclusively, useful for applying tissue sealant agents to biological tissue to effect hemostasis or achieve other therapeutic results. More particularly, it relates to spray application of tissue sealants from a hand-held applicator.
2. Description of Related Art Including Information Disclosed under 37 CFR 1.97 and 37 CFR 1.98
Use of tissue sealants and other biological materials is an important emerging surgical technique, well adapted for the operating room or field environments such as the doctor""s office or mobile medical units. Preferred sealants include fibrin sealants which are formed from blood plasma components and comprise, on the one hand, a first agent containing fibrinogen and Factor XIII and on the other hand a second agent which usually includes thrombin, and calcium ions. The fibrinogen is capable of a polymerizing and being cross-linked to form a solid fibrin clot when the agents are mixed. The necessary additional factors to simulate relevant portions of the natural blood coagulation cascade are suitably distributed between the fibrinogen and thrombin agents.
High levels of protection against transmission of infections or induction of immunological reactions can be assured by using an autologous or single-donor source for both agents. Such sealants are highly effective, are biologically degraded without residue and may promote wound healing.
Depending upon the potency of the particular formulations employed, coagulation of the sealant may take place very rapidly, yielding a gel within perhaps 10 or 20 seconds. Though often very desirable for surgical reasons, such fast-acting properties present potential problems of fouling or clogging. These problems must be overcome in devising suitable applicators, and methods of application.
A popular manually operable applicator for such two-agent sealants employs a dual syringe construction wherein two syringes, connected by a yoke, each provide a reservoir for one of the agents. In most prior devices, the sealant agents are discharged in separate streams and mixed externally of the applicator. Such applicators are similar in principle to household epoxy glue applicators commonly available in hardware stores. Achieving effective mixing externally of the applicator is problematic.
In U.S. Pat. No. 5,266,877, and the above applications, the present inventor teaches various constructions of a dual syringe applicator wherein the fluid sealant agents are mixed internally.
In one or more of the above copending applications the possibility of retrograde clearing of the mixed fluids pathway within the applicator, using suction, is also disclosed. The applicator is provided with suitable suction conduits and valving to apply suction to the work surface, to prepare it for the application of sealant, for example by removing fluids. As taught, the valving is operable to effect retrograde clearing of a sealant dispensing pathway. Enhanced mixing results and problems of fouling by deposited solids are avoided.
Such devices are useful primarily for localized tissue treatment to close wounds and the like. More widespread events, such as diffuse oozing and sealing of tissues to prevent fluid leaks, are better treated by spray applicators and a number have been proposed with varying degrees of complexity and success.
Most prior proposals for spray applicators, including applicant""s own invention disclosed in a patent application Ser. No. 09/037,160 Case GE 1110, abide by the principle of external mixing because of the difficulties inherent in internal mixing. The problem of discharging a rapidly coagulating stream of mixed sealant agents through the narrow valves and orifices typically employed in spray dispensers, while preventing the applicator clogging and becoming unusable, is imposing. The problem is compounded when it is realized that such applicators are intended for occasional use: they may be used in short bursts of a few seconds each, being then set down to be used again several minutes later, providing plenty of opportunity for residual sealant to clog the applicator.
Capozzi et al. U.S. Pat. No. 5,116,315 discloses a spray applicator that outputs a mixture of two sealant agents which applicator is provided with replaceable spray orifices so that when they become clogged with sealant, the user can remove the clogged orifice and replace it with a new one. Changing the clogged orifices is inconvenient and may be difficult and inconvenient during surgery. Fibrin sealants can coagulate very quickly, in a matter of seconds. Accordingly, such a spray applicator can easily become clogged between applications if it is set down for a minute or two. The need to change the spray orifices during a surgical procedure, and to have replacement orifices available, may be quite disruptive or impractical.
Furthermore, the momentum of the spray droplets leaving the applicator is derived from manually applied pressure to the sprayed liquid. Naturally, the pressure with which the liquid is applied to the spray orifice, and therefore the momentum with which the droplets are discharged from the spray orifice, is subject to variation, caused by the mechanics of the dispensing mechanism or simple inability of a human operator to apply constant pressure throughout a range of manual movement. Accordingly with the Capozzi spray applicators, it is difficult to produce an even spray having a consistent spray pattern. It is also difficult to discharge the droplets from the applicator with a constant momentum, as would be desirable for consistent application of materials such as a surgical sealant.
Prior to the present invention, a solution to this problem has been to apply the individual sealant agents in overlapping spray patterns, with the intention that the agents will mix in the air or on the tissue surface. Thus, for example, Redl U.S. Pat. No. 4,359,049 discloses a dual syringe tissue adhesive applicator for dispensing two adhesive agents, which applicator employs a disposable mixing needle to provide a mixed sealant output a in the form of a liquid stream or a series of droplets. To provide a spray output, FIGS. 4 and 5 of Redl disclose the use of two pressurized gas streams emerging from outlets 50,51 in the region of the valves 43,44 of conveying channels 41,40 which separately supply adhesive agents from syringe bodies 1 and 2. (See column 3, lines 40-47.) Two spray patterns are generated and, according to Redl xe2x80x9cunite at a distance of about 10 to 20 cm, rapidly forming a thin uniform adhesive film on the surface to be adhered or sealed.xe2x80x9d, see column 4 lines 1-3.
Pursuant to the present invention, it has been discovered that sealant agents discharged in separate sprays do not mix effectively. Apparently, the individual agents are frequently deposited on a work surface as individual or isolated drops or droplets that are unable to coalesce with droplets of the complementary agent. Thus mixing may be incomplete or, at best, slow. A further difficulty is that of maintaining a high degree of overlap of spatially separated sprays. Droplets deposited outside the zone of overlap are not combined with the complementary agent and therefore are not useful: valuable sealant product is wasted. Additionally, because the agents are not optimally mixed the resultant sealant may lack adhesive or cohesive strength.
There is accordingly a need for a sealant spray applicator, and method of applying a multi-agent sealant, which can effectively deliver multiple sealant agents to a work surface, for example a biological tissue, in an efficiently mixed state.
The present invention solves the problem of providing a sealant spray applicator, and method of applying a multi-agent sealant, which can effectively deliver multiple sealant agents to a work surface, for example a biological tissue, in an efficiently mixed state.
In one aspect, the invention provides a spray applicator for a liquid sealant comprising multiple sealant agents at least two of which are complementary one to the other and polymerize when mixed, the applicator comprising a sealant dispensing pathway terminating in a dispensing orifice through which the sealant agents are dispensed and a gas-entrainment chamber wherein mixed fluid sealant from the dispensing orifice is entrained in a gas stream for delivery to the work surface. Preferably a retrograde clearing device can be operated to apply suction to the sealant dispensing pathway, between applications of sealant, to remove clogs therefrom.
In another aspect the invention provides a method of spraying liquid sealant agents on to a work surface comprising mixing the liquid sealant agents in the liquid state and discharging the mixed liquid into a gas stream for dispersion of the liquid into droplets and delivery to the work surface. Optionally, the method can include a suction clearing step, between spray applications, to remove undesired deposits of mixed sealant.
By actively mixing the sealant agents prior to spraying ,the invention can assure that an effective sealant composition reaches the work surface and deposit of unmixed agents is avoided. Such active premixing is also helpful in initiating coagulation and thus providing a fast-acting sealant process. Furthermore, wasteful deposit on the work surface, of unmixed sealant agents, which will not coagulate into sealant, is avoided.
Use of a pressurized gas source to impel the spray facilitates generation of a constant velocity spray for even application of the sealant. It is difficult to obtain a steady spray by manually pressurizing of liquid sealant, as is required by conventional applicators such as those taught by Capozzi.
Preferably, although not necessarily, the sealant is a biological sealant, for example a tissue adhesive, and the work surface is a biological tissue subject to surgery. The sealant agents comprise a first, structural agent capable of gelling, and preferably of solidification and a second, activation agent which activates such gelling and, optionally, solidification. More preferably, the sealant is a tissue sealant and the first agent comprises fibrinogen and the second agent comprises, or can generate a fibrinogen activator, especially thrombin or an equivalent thereof.